15.1 Handling of unknown operations
29.0023GPPMobile Application Part (MAP) specificationRelease 17TS
Unknown operations (i.e. a standard operation introduced in a later version of the MAP specification, or a private operation) can be introduced into MAP in a backwards compatible way. This means that the receiver of an unknown operation shall, if the dialogue state allows it, send a TC-REJECT component to the sender of the operation indicating ‘unrecognised operation’ and continue with the processing of further components or messages exchanged within the dialogue as if the unknown operation had not been received.
The standardised structure of a MAP dialogue shall not be affected by the invocation of unknown operations, i.e. if a dialogue uses only a TC-BEGIN message which is acknowledged by a TC-END message, a TC-CONTINUE message shall not be used to invoke an unknown operation. However the standardised structure of a MAP dialogue may be affected by the rejection of unknown operations, i.e. if a dialogue uses only a TC-BEGIN message which is acknowledged by a TC-END message, a TC-CONTINUE message followed by a TC-END message may be used to carry the rejection of an unknown operation and the response to the standardised operation. The entity which initiated a dialogue whose standardised structure is a TC-BEGIN message which is acknowledged by a TC-END message shall not send any messages in that dialogue after the TC-BEGIN. Note that if the dialogue structure is affected as described in this paragraph the TC-CONTINUE shall include the dialogue portion required to confirm the acceptance of the dialogue.
Unknown operations may be invoked in the following types of message (there is no restriction as to how many unknown operations can be invoked in a message):
– TC-BEGIN: the component to invoke the unknown operation shall follow the component of the standard operation which is included in this message.
– TC-CONTINUE: the component to invoke the unknown operation may be transported as the only component in a stand-alone message or may be grouped with existing operations. In the latter case a specific sequencing of components is not required.
– TC-END: if the component to invoke the unknown operation is grouped with an existing operation a specific sequencing of components is not required
The TC-REJECT component may be sent in the following messages:
– TC-CONTINUE or TC-END: either as the only component of the message or grouped with an existing component. The choice is up to the MAP-Service User.
If the received message contains only unknown operations the MAP-Service User shall send the TC-REJECT components in a TC-CONTINUE message to the peer entity, if the dialogue state allows it.
If the received message contains unknown operations and standard operations and the standardised structure of the dialogue requires the response to the standard operation to be sent within a TC-END message, then the MAP-Service User may send the response to the standard operations and the TC-REJECT components for the unknown operations in a TC-CONTINUE message followed by a TC-END message. Neither a specific distribution of the components to the TC messages nor a specific sequencing of components is required.
Note that the SDL diagrams of clauses 19 – 25 do not show the report to the MAP-Service User about the reception of the unknown operation. This has been done for simplicity of description; the MAP PM may inform the MAP-Service User.
The sender of the unknown operation shall ensure that there is enough room in the used message for the unknown operation.